This invention relates generally to photolithography in semiconductor manufacturing and more particularly to a system and method for providing a lithographic light source for a semiconductor manufacturing process.
Photolithographic fabrication of semiconductor components, such as integrated circuits and dynamic random access memory chips, is customary in the semiconductor industry. In photolithographic fabrication, light may be used to cure or harden a photomask that is used to form a pattern of conductive, semiconductive, and insulative components in the semiconductor layer. The resulting pattern of conductive, semiconductive, and insulative components on the semiconductor layer form extremely small microelectronic devices, such as transistors, diodes, and the like. The microelectronic devices are generally combined to form various semiconductor components.
The density of the microelectronic devices on the semiconductor layer may be increased by decreasing the size or geometry of the various conductive, semiconductive, and insulative components formed on the semiconductor layer. This decrease in size allows a larger number of such microelectronic devices to be formed on the semiconductor layer. As a result, the capability and speed of the semiconductor component may be greatly improved.
The lower limit on the size, often referred to as the line width, of a microelectronic device is generally limited by the wavelength of light used in the photolithographic process. The shorter the wavelength of light used in the photolithographic process, the smaller the line width of the microelectronic device that may be formed on the semiconductor layer. Semiconductor component fabrication may be further improved by increasing the intensity of the light used in the photolithographic process, which reduces the time the photomask material needs to be radiated with light. As a result, the semiconductor components may be produced faster and less expensively.
Extreme ultraviolet (EUV) light has a very short wavelength and is preferable for photolithographic fabrication of semiconductor components. Conventional systems for generating EUV light typically include an energy source impinging on a hard target. The energy source may be a high energy laser, an electron beam, an electrical arc, or the like. The hard target is generally a ceramic, thin-film, or solid target comprising materials such as tungsten, tin, copper, gold, xenon, or the like. Optics, such as mirrors and lenses, are used to reflect and focus the EUV light on a semiconductor layer.
Conventional systems and methods for generating EUV light suffer from numerous disadvantages. One of these disadvantages is that debris from the energy source/target interaction is produced along with the EUV light. The production of debris, which increases with the intensity of the energy source, results in the target being degraded and eventually destroyed. The debris may coat and contaminate the optics and other components of the system, thereby reducing efficiency and performance while increasing frequency of maintenance and length of down time.
Recent improvements in systems and methods for generating EUV light include an energy source impinging on a fluid target. However, these systems and methods also suffer from disadvantages. One disadvantage is the existence of plasma-induced erosion. The energy source impinging on the fluid target produces a plasma which can degrade the external surfaces of the components of the light source. This plasma-induced erosion releases contaminants that must be removed, adding cost and complexity to the system.
Another disadvantage is that the plasma is a major source of high heat loading on the components of the light source. Thermal particle or ion impact from the plasma further adds to the high radiative heat load on the components. This problem is compounded by the fact that the amount of heat that can be removed from the components is limited by their severe geometric restrictions.
Yet another disadvantage is caused by the collection optics needing a direct view of the plasma to collect the light rays being generated. This results in direct plasma interaction on the collection optics which causes erosion. The optics are sensitive to erosion and costly to repair.
In accordance with the present invention, a system and method for providing a lithographic light source are provided that substantially eliminate or reduce the disadvantages or problems associated with previously developed methods and systems. In particular, the present invention provides a coaxial shielding fluid 360xc2x0 around a process fluid.
In one embodiment of the present invention, a method for providing a lithographic light source is provided that includes producing a process fluid plume. A coaxial shielding fluid is produced around the process fluid plume. A plasma is generated by providing an energy source that impinges on the process fluid plume.
In another embodiment of the present invention, a method for manufacturing a semiconductor device is provided that includes depositing a photoresist layer over a semiconductor target. A process fluid is produced in a lithographic system. A coaxial shielding fluid is produced around the process fluid. A light is produced by focusing an energy source on the process fluid. A photoresist mask is formed by exposing at least a portion of the photoresist layer to the light.
In a third embodiment of the present invention, a system for providing a lithographic light source is provided that includes an energy source, a fluid system, and an optics system. The fluid system includes a diffuser, a holder assembly, and a nozzle system. The nozzle system is operable to produce a process fluid and a coaxial shielding fluid. The optics system is operable to focus the energy source on the process fluid and to transmit the photolithographic light generated by the plasma onto a semiconductor chip.
Technical advantages of the present invention include providing a coaxial shielding fluid for a lithographic light source. In particular, a coaxial shielding fluid is introduced in the same direction as the process fluid and 360xc2x0 around the outside of the process fluid outlet. As a result, a minimal quantity of shielding fluid is required and vacuum pumping needs for fluid separation are reduced. Improved shielding is provided because the shielding fluid is relatively dense close to the plasma, increasing the ability of the shielding fluid to absorb kinetic energy from the particles emanating from the plasma. The shielding fluid also reduces the lateral spread of the process fluid plume. This increases the efficiency of the diffuser, thereby lowering pumping costs.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, description and claims.